kunleade

2011 GL450. I had no communication with rear SAM, which disabled turn signals, wiper front cigarette lighter, lift gate and what-not. So I decided to remove the rear SAM, suspecting water might have got in there. Wound all windows down and didn’t remove battery cable while at it (lesson learned). While taking out the rear SAM the metal holder came in contact with a bolt on the fuse box in the trunk, which caused an electrical spark.

Rear SAM has some water damage to one attachment. Cleaned and put it back.

Since the spark, engine cranks but no start. Windows controls do not work (been covering the windows with tarp). OBD2 port does not work. I tested most of the fuses in the luggage compartment, in the engine compartment and the fuse box in the front passenger side and they are okay.

I’m at my wit’s end. Any help is appreciated.

DennisG01

I'm probably not the one to really dive deep into this to help, but I noticed you said you tested "most" of the fuses. I would at least start there and verify "all" the fuses and relays.

Other than that, I would assume that hooking up a STAR computer may lend some insight to what's going on. Or, at least point you in the direction of what system(s) aren't responding. Someone else can talk more about that, though.

chassis

Because of the hot wire touching ground, you need to verify all fuses in the vehicle. Dig out the fuse diagram (paper), it's usually under the rear (second row) passenger seat tucked into one of the fuse boxes. Verify each and every fuse in the vehicle.

Miguk_Saram

+1

In the mean time, for your windows, just disconnect the driver's side window controls and apply 12v directly to each contact on the harness to get them to raise

Use a Multi-meter to determine which lead is ground (test for continuity), then it's just a matter of connecting the negative to ground and the positive to each of the other leads, one-at-a-time. If I am not mistaken, switching polarity controls raising vs lowering.

kunleade

I said "most" of the fuses because I'm not able to reach the fuses in the battery compartment to test. Every other fuse in other locations were tested and all good.

kunleade

Thanks for the tip on raising the windows!
Would you know how I can move the front passenger seat forward so I can access the battery compartment under the seat?

kunleade

The OBD2 port is not functioning. Is there another location (in the engine compartment maybe?) where I can hook up the computer for diagnosing the problem?

DennisG01

If there is, it must be hidden awfully well 'cause I've never seen it or heard of it!

You can unbolt the passenger seat - it's pretty simple and straight forward.

Miguk_Saram

There are 4 torx screws that hold the seats in position, one at each corner. The plastic covers slide forward/backward with very little effort to reveal the screws. It might be a bit tricky to remove all the screws if you cant move the seat, but certainly doable. Just loosen the bolt as much as possible with the ratchet, then use a suitable wrench the rest of the way.

If the current position of the seat does not grant easy access, then you can disconnect the widest wiring harness under the respective seat and, as with the windows, apply 12v directly to the proper lead (sorry, I am not sure which lead that is). One note of caution: there are 3+ harnesses under each seat, the chrome harness is for SRS (seatbelts), once unplugged you would normally need to reset the SRS warning light via OBD (this may not be a problem at this point since your OBD does not seem to be functional).

Now, back to the SAM removal.

If the short occurred during removal of the SAM, there's a good chance your problem lies in the SAM itself. For reference, the following thread discusses the rear SAM wiring and has a .pdf with a wiring diagram:

https://mbworld.org/forums/gl-class-...am-wiring.html

kunleade

Thanks! Will do just that.

kunleade

Update:
I took the car to the dealership. The pre-fuse in the battery compartment was blown from the spark, causing the car not to start. Rear SAM and the pre fuse box were replaced and everything works fine. Cost about $2500, most of it being labor charges.

I think water got onto the rear SAM board again: driver side reverse light stays on even when engine is off and the fuel gauge stopped working. May need to go to dealership again as the rear SAM is still under warranty.

Max Blast

Ouch

chassis

Have the rear taillamp gaskets been replaced? These are the common water infiltration sources. Have the sunroof drains been checked? Liftgate perimeter seal?